The research proposed in this program project includes the study of processes underlying the acquisition of language and research on language training for retarded children. The language process research is concerned with the study of variables controlling the development of language and language functions. Included in the study of variables controlling the development of language, are studies in auditory perception and discrimination, the development of the phonological system from a distinctive feature viewpoint, studies on imitation and language learning and the study of relationships between concept development and the acquisition of syntax. The research on language functions focuses primarily on study of strategies utilized in verbal learning. The research on language training of the retarded children encompasses the study of training of pre-language skills such as imitation training and direction following as well as research into procedures and rules for the training gf morphological inflections, basic syntax and semantic relationships and training in the use of non-verbal and suprasegmental features in face to face communication.